The Latin word persona was originally used to denote the mask worn by an actor. From this it was applied to the role he assumed, and, finally, to any character on the stage of life, to any individual. This article discusses (1) the definition of "person", especially with reference to the doctrine of the Incarnation; and (2) the use of the word persona and its Greek equivalents in connection with the Trinitarian disputes. For the psychological treatment see PERSONALITY.

Substantia — "Substance" is used to exclude accidents: "We see that accidents cannot constitute person" (Boethius, op. cit.). Substantia is used in two senses: of the concrete substance as existing in the individual, called substantia prima, corresponding to Aristotle's ousia prote; and of abstractions, substance as existing in genus and species, called substantia secunda, Aristotle's ousia deutera. It is disputed which of the two the word taken by itself here signifies. It seems probable that of itself it prescinds from substantia prima and substantia secunda, and is restricted to the former signification only by the word individua.

Individua —Individua, i.e., indivisum in se, is that which, unlike the higher branches in the tree of Porphyry, genus and species, cannot be further subdivided. Boethius in giving his definition does not seem to attach any further signification to the word. It is merely synonymous with singularis.

Rationalis naturae — Person is predicated only of intellectual beings. The generic word which includes all individual existing substances is suppositum. Thus person is a subdivision of suppositum which is applied equally to rational and irrational, living and non-living individuals. A person is therefore sometimes defined as suppositum naturae rationalis.

The definition of Boethius as it stands can hardly be considered a satisfactory one. The words taken literally can be applied to the rational soul of man, and also the human nature of Christ. That St. Thomas accepts it is presumably due to the fact that he found it in possession, and recognized as the traditional definition. He explains it in terms that practically constitute a new definition. Individua substantia signifies, he says, substantia, completa, per se subsistens, separata ab aliia, i.e., a substance, complete, subsisting per se, existing apart from others (III, Q. xvi, a. 12, ad 2um).

If to this be added rationalis naturae, we have a definition comprising the five notes that go to make up a person: (a) substantia— this excludes accident; (b) completa— it must form a complete nature; that which is a part, either actually or "aptitudinally" does not satisfy the definition; (c) per se subsistens—the person exists in himself and for himself; he is sui juris, the ultimate possessor of his nature and all its acts, the ultimate subject of predication of all his attributes; that which exists in another is not a person; (d) separata ab aliis—this excludes the universal, substantia secunda, which has no existence apart from the individual; (e) rationalis naturae—excludes all non-intellectual supposita.

To a person therefore belongs a threefold incommunicability, expressed in notes (b), (c), and (d). The human soul belongs to the nature as a part of it, and is therefore not a person, even when existing separately. The human nature of Christ does not exist per se seorsum, but in alio, in the Divine Personality of the Word. It is therefore communicated by assumption and so is not a person. Lastly the Divine Essence, though subsisting per se, is so communicated to the Three Persons that it does not exist apart from them; it is therefore not a person.

Theologians agree that in the Hypostatic Union the immediate reason why the Sacred Humanity, though complete and individual, is not a person is that it is not a subsistence, not per se seorsum subsistens. They have, however, disputed for centuries as to what may be the ultimate determination of the nature which if present would make it a subsistence and so a person, what in other words is the ultimate foundation of personality. According to Scotus, as he is usually understood, the ultimate foundation is a mere negation. That individual intellectual nature is a person which is neither of its nature destined to be communicated—as is the human soul—nor is actually communicated—as is the Sacred Humanity. If the Hypostatic Union ceased, the latter would ipso facto, without any further determination, become a person. To this it is objected that the person possesses the nature and all its attributes. It is difficult to believe that this possessor, as distinct from the objects possessed, is constituted only by a negative. Consequently, the traditional Thomists, following Cajetan, hold that there is a positive determination which they call the "mode" of subsistence. It is the function of this mode to make the nature incommunicable, terminated in itself, and capable of receiving its own esse, or existence. Without this mode the human nature of Christ exists only by the uncreated esse of the Word.

Suarez also makes the ultimate foundation of personality a mode. In his view, however, as he holds no real distinction between nature and esse, it does not prepare the nature to receive its own existence, but is something added to a nature conceived as already existing. Many theologians hold that the very concept of a mode, viz., a determination of a substance really distinct from it but adding no reality, involves a contradiction. Of more recent theories that of Tiphanus ("De hypostasi et persona", 1634) has found many adherents. He holds that a substance is a suppositum, an intelligent substance a person, from the mere fact of its being a whole, totum in se. This totality, it is contended, is a positive note, but adds no reality, as the whole adds nothing to the parts that compose it. In the Hypostatic Union the human nature is perfected by being assumed, and so ceases to be a whole, being merged in a greater totality. The Word, on the other hand, is not perfected, and so remains a person. Opposing theologians, however, hold that this notion of totality reduces on analysis to the Scotistic negative. Lastly the neo-Thomists, Terrien, Billot, etc., consider personality to be ultimately constituted by the esse, the actual existence, of an intelligent substance. That which subsists with its own esse is by that very fact incommunicable. The human nature of Christ is possessed by the Word and exists by His infinite esse. It has no separate esse of its own and for this reason is not a person. The suppositum is a suppositum as being ens in the strictest sense of the term. Of all Latin theories this appears to approach most nearly to that of the Greek fathers. Thus in the "Dialogues of the Trinity" given by Migne among the works of St. Athanasius, the author, speaking of person and nature in God, says: He gar hypostasis to einai semainei he de theotes to ti einai (Person denotes esse, the Divine nature denotes the quiddity; M. 28, 1114). An elaborate treatment is given by St. John Damascene, Dial. xlii.

(2) The use of the word persona and its Greek equivalents in connection with the Trinitarian disputes

For the constitution of a person it is required that a reality be subsistent and absolutely distinct, i.e. incommunicable. The three Divine realities are relations, each identified with the Divine Essence. A finite relation has reality only in so far as it is an accident; it has the reality of inherence. The Divine relations, however, are in the nature not by inherence but by identity. The reality they have, therefore, is not that of an accident, but that of a subsistence. They are one with ipsum esse subsistens. Again every relation, by its very nature, implies opposition and so distinction. In the finite relation this distinction is between subject and term. In the infinite relations there is no subject as distinct from the relation itself; the Paternity is the Father—and no term as distinct from the opposing relation; the Filiation is the Son. The Divine realities are therefore distinct and mutually incommunicable through this relative opposition; they are subsistent as being identified with the subsistence of the Godhead, i.e. they are persons. The use of the word persona to denote them, however, led to controversy between East and West. The precise Greek equivalent was prosopon, likewise used originally of the actor's mask and then of the character he represented, but the meaning of the word had not passed on, as had that of persona, to the general signification of individual. Consequently tres personae, tria prosopa, savoured of Sabellianism to the Greeks. On the other hand their word hypostasis, from hypo-histemi, was taken to correspond to the Latin substantia, from sub-stare. Tres hypostases therefore appeared to conflict with the Nicaean doctrine of unity of substance in the Trinity. This difference was a main cause of the Antiochene schism of the fourth century (see MELETIUS OF ANTIOCH). Eventually in the West, it was recognized that the true equivalent of hypostasis was not substantia but subsistentia, and in the East that to understand prosopon in the sense of the Latin persona precluded the possibility of a Sabellian interpretation. By the First Council of Constantinople, therefore, it was recognized that the words hypostasis, prosopon, and persona were equally applicable to the three Divine realities. (See INCARNATION; NATURE; SUBSTANCE; TRINITY.)